10 Common Planning Permission Mistakes (And How to Avoid Them)

Securing planning permission can be one of the most stressful stages in any development project.

Whether you’re building an extension, converting a loft, or developing a new site, one small oversight can delay your timeline—or derail it completely. At Cubed Design Studios, we’ve helped countless clients navigate this process smoothly. Here are the 10 most common planning permission mistakes—and how you can avoid them.

1. Failing to Check Local Planning Policy

Every council has different development rules. Before designing anything, check your Local Planning Authority’s guidelines to avoid wasting time on an unapprovable concept.

2. Assuming Permitted Development Rights Always Apply

Just because your neighbour didn’t need permission doesn’t mean you won’t. Flats, conservation areas, and previous planning history can remove permitted development rights entirely.

3. Submitting Incomplete Applications

One missing document or unchecked box can lead to refusal. Ensure you’ve included site plans, elevation drawings, ownership certificates, and a proper design and access statement.

4. Ignoring Pre-Application Advice

Most councils offer pre-app services. Getting feedback before formally submitting your plans can save you time, money, and multiple rejections.

5. Poorly Drawn or Inaccurate Plans

Low-quality or vague drawings are one of the top reasons for delays. At Cubed Design Studios, we ensure your application is professionally drawn and presentation-ready.

6. Not Considering Impact on Neighbours

Loss of light, privacy, or overbearing structures can trigger objections. We always advise a sensitivity analysis of nearby buildings and sightlines.

7. Underestimating the Timeframe

Standard decisions take up to 8 weeks—longer if your application is complex or contested. Plan ahead and don’t schedule contractors before you get approval.

8. Failing to Budget for Application Fees

Each submission comes with a council fee, which varies by project type. Budget for this early, and account for potential re-submissions or appeals.

9. Making Big Changes After Submission

Changing the design mid-review resets the process or gets your application invalidated. Work out the key details in advance or wait until a decision before amending.

10. Going It Alone Without Professional Guidance

DIY applications often overlook crucial planning policies. Working with a studio like Cubed Design ensures your application is comprehensive and has the best chance of success.

Need Help with Planning Permission?

At Cubed Design Studios, we handle the entire process—from drawings to submission, appeals, and negotiations. We tailor your application to your council’s specific expectations and help you avoid costly mistakes.